In optical fiber cables for high-speed mass data transmission, optical fiber ribbons, in which a plurality of optical fiber strands are arranged in parallel and bonded together, are used to simplify cable packaging and operations.
When splicing or the like of such optical fiber ribbons, an optical fiber holding member is used for holding the optical fiber. In particular, for splicing or the like each of the optical fibers in the optical fiber ribbon collectively, it is required to collectively hold a plurality of the optical fibers.
As such an optical fiber holding member, Japanese Unexamined Patent Application Publication No. 2007-57698 (JP-A-2007-57698) discloses an optical fiber holding member having a groove formed in a longitudinal direction of a main body thereof, in which an optical fiber is placed inside the groove and, when a lid is closed, a protruded portion disposed on an inner surface of the lid presses and holds the optical fiber.
FIG. 13A is a plan view showing a conventional optical fiber holding member 100. The optical fiber holding member 100 mainly includes a main body section 101 and a lid section 103. An upper surface of the main body section 101 has a groove 105 formed in a longitudinal direction thereof.
The main body section 101 is provided with a lid section 103 that can be freely opened and closed by means of a hinge mechanism. A pressing member 107 is provided on an inner surface side of the lid 103 (a surface facing the main body section 101). The pressing member 107 is made of resin, for example. The pressing member 107 is disposed at a position in such a manner that the pressing member 107 covers over the groove 105 when the lid section 103 is closed.
The lid section 103 is made of iron, for example. A magnet 109 is disposed at a position facing the lid section 103 when the lid section 103 is closed. Thus, when the lid section 103 is closed, the magnet attracts the lid section 103 and the lid section 103 can be kept closed. At this time, since the lid section 103 is attracted to the main body section 101, the pressing member 107 is pressed against the main body section 101.
FIG. 13B is a drawing showing the optical fiber holding member 100 with an optical fiber ribbon 111 disposed therein. The optical fiber ribbon 111 includes a plurality of optical fibers provided side by side and unified. A width of the groove 105 corresponds to a width of the optical fiber ribbon 111 used. Thus, the groove 105 determines the position of the optical fiber ribbon 111 in its width direction.
FIG. 14A is a plan view showing a state in which the lid section 103 is closed and FIG. 14B is a cross section of X section taken along Y-Y line in FIG. 14A. As mentioned above, the optical fiber ribbon 111 is disposed in the groove 105. Here, the depth of the groove 105 is less than the thickness of the optical fiber ribbon 111 (an outer diameter of the optical fiber forming the optical fiber ribbon 111). Thus, some parts of the optical fiber ribbon 111 protrude above the groove 105.
Also, as mentioned above, the pressing member 107 is disposed over the groove 105 and is pressed against the main body section 101 side. Thus, the pressing member 107 presses the optical fiber ribbon 111. That is, the optical fiber holding member 100 holds the optical fiber ribbon 111.
With the optical fiber ribbon 111 held in this way, it is possible to prevent shifting of the optical fiber ribbon 111 in its axial direction with respect to the optical fiber holding member 100. Thus, it is easy to perform operations such as cutting, coat peeling, and splicing optical fiber ribbons, for example.
However, in recent years, optical fiber ribbons in which optical fibers arranged side by side are bonded intermittently in its longitudinal direction have been in use (JP-A-2007-279226, for example). Such intermittent bonding of optical fibers is characterized in improved line concentration density, reduced transmission loss due to bending, simplified procedure for turning into single cores, and the like.
In such optical fiber ribbons, adjacent optical fibers do not fully tied up with each other and the optical fibers can be partially separated from each other. Thus, if the optical fiber ribbon 111 mentioned above is an intermittently bonded ribbon, then the optical fibers may spread out in its width direction.
FIG. 15 is a drawing showing a state in which some of the optical fibers ride over the groove 105 when the optical fiber ribbon 111 as above is used and the optical fibers spread in the width direction. If some of the optical fibers are pushed out of the groove 105 in this way, it is impossible for the pressing member 107 to keep down all the optical fibers uniformly with certainty and to hold the optical fiber ribbon 111 sufficiently. Also, since only the optical fiber riding over the groove is pressed strongly, there is a possibility that the optical fiber may break or the like.
To counter this problem, there is a method to prevent riding over of the optical fiber by increasing a depth of the groove 105. However, if the depth of the groove 105 is increased, the protrusion margin of the optical fiber ribbon 111 above the groove 105 would disappear and it would be impossible for the pressing member 107 to apply sufficient pressing force to the optical fiber ribbon.